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A stationary charge creates and interacts with the electric field, while a moving charge creates a magnetic field.
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Area of Science:

  • Condensed matter physics
  • Mesoscopic physics
  • Quantum transport

Background:

  • Johnson-Nyquist noise arises from intrinsic conductivity in electron liquids.
  • Electron density fluctuations occur in charge-neutral graphene devices.
  • External electric and magnetic fields influence charge density and current.

Purpose of the Study:

  • To investigate the impact of electron density fluctuations on graphene conductivity.
  • To develop a quantitative theory for the fluctuation contribution to macroscopic conductivity (σfl).
  • To analyze the behavior of σfl under varying magnetic fields.

Main Methods:

  • Theoretical modeling of hydrodynamic flow induced by charge fluctuations.
  • Analysis of the fluctuation contribution to conductivity (σfl).
  • Investigation of the system size and magnetic field dependence of σfl.

Main Results:

  • Electron density fluctuations induce a fluctuation contribution to conductivity (σfl).
  • σfl exhibits logarithmic divergence with system size at zero magnetic field.
  • σfl is rapidly suppressed by relatively small magnetic fields, resulting in giant magnetoresistance.

Conclusions:

  • Fluctuations driven by Johnson-Nyquist noise significantly impact graphene conductivity.
  • The developed theory quantitatively describes the fluctuation-induced conductivity.
  • Giant magnetoresistance in graphene is a consequence of magnetic field suppression of these fluctuations.